# US 2019/0314751 A1 · Air filter with visual filter life indicator zone and sorbent-loaded visual reference zone > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0314751 A1 - Document ID: US20190314751A1 - Status: Published application - Kind: A1 - Application number: 16/348,254 - Filed: 2016-11-17 - Published: 2019-10-17 - Earliest claimed: 2016-11-17 - Assignees: 3M Innovative Properties Company - Applicants: 3M Innovative Properties Company - Inventors: Liang Cheng; Andrew R. Fox; Himanshu Jasuja; Zhiqun Zhang - Web page: https://patentgrep.com/patent/US20190314751A1 ## CPC - B01D 46/0086: {Filter condition indicators} - B01D 29/13: Supported filter elements - B01D 35/143: Filter condition indicators - B01D 46/00: Filters or filtering processes specially modified for separating dispersed particles from gases or vapours (filtering elements B01D24/00-B01D35/00; filtering material B01D39/00; their regeneration outside the filters B01D41/00) - B01D 46/0032: {using electrostatic forces to remove particles, e.g. electret filters} - B01D 46/0036: {by adsorption or absorption} - B01D 46/10: Particle separators, e.g. dust precipitators, using filter plates, sheets or pads having plane surfaces - B01D 46/521: {using folded, pleated material} - B01D 46/62: connected in series - B01D 53/04: with stationary adsorbents {(B01D53/025 takes precedence)} - B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28) ## Abstract An air filter (1) comprises an air filter media (10) with a sorbent-free area (20) that provides a visual filter life indicator zone (30) and with a sorbent-loaded area (26) that provides a visual reference zone (27). ## Claims ### Claim 1 An air filter comprising an air filter media that comprises a visual filter life indicator zone and a visual reference zone, the air filter media comprising: a nonwoven fibrous filtration web comprising at least some fibers that comprise charged electret moities, wherein the nonwoven fibrous filtration web comprises a first major surface with an active particle-filtration area that includes at least one sorbent-free area and at least one sorbent-loaded area, wherein the at least one sorbent-free area is configured to provide a visual filter life indicator zone of the air filter, and wherein the at least one sorbent-loaded area is configured to provide a visual reference zone for the visual filter life indicator zone. ### Claim 2 (depends on 1) The air filter of claim 1 wherein in the sorbent-loaded area, sorbent particles are adhesively bonded to fiber portions that provide the first major surface of the nonwoven fibrous filtration web. ### Claim 3 (depends on 1) The air filter of claim 1 wherein the at least one sorbent-loaded area occupies at least about 50 percent of the active particle-filtration area of the first major surface of the nonwoven fibrous filtration web, and wherein the at least one sorbent-free area occupies at most about 50 percent of the active particle-filtration area of the first major surface of the nonwoven fibrous filtration web. ### Claim 4 (depends on 1) The air filter of claim 1 wherein the at least one sorbent-loaded area occupies at least about 70 percent of the active particle-filtration area of the first major surface of the nonwoven fibrous filtration web, and wherein the at least one sorbent-free area occupies at most about 30 percent of the active particle-filtration area of the first major surface of the nonwoven fibrous filtration web. ### Claim 5 (depends on 1) The air filter of claim 1 wherein in the at least one sorbent-loaded area, sorbent particles are present on the first major surface of the nonwoven fibrous filtration web at a loading of at least about 60 grams per square meter, and wherein in the at least one sorbent-free area, sorbent particles are present on the first major surface of the nonwoven fibrous filtration web at a loading of at most about 5 grams per square meter. ### Claim 6 (depends on 1) The air filter of claim 1 wherein in the at least one sorbent-loaded area, sorbent particles are present on the first major surface of the nonwoven fibrous filtration web at a loading of at least about 80 grams per square meter, and wherein in the at least one sorbent-free area, sorbent particles are present on the first major surface of the nonwoven fibrous filtration web at a loading of at most about 1 grain per square meter. ### Claim 7 (depends on 1) The air filter of claim 1 wherein the sorbent-loaded area comprises primary sorbent particles that are mixed with one or more types of secondary sorbent particles. ### Claim 8 (depends on 1) The air filter of claim 1 wherein in the at least one sorbent-loaded area, sorbent particles are present that comprise at least some of activated carbon particles. ### Claim 9 (depends on 8) The air filter of claim 8 wherein the activated carbon particles exhibit a mesh size that is from about 20 mesh to about 100 mesh. ### Claim 10 (depends on 1) The air filter of claim 1 wherein the at least one sorbent-free area is provided in the form of a plurality of discrete sorbent-free areas. ### Claim 11 (depends on 1) The air filter of claim 1 wherein the at least one sorbent-loaded area is provided in the form of a plurality of discrete sorbent-loaded areas. ### Claim 12 (depends on 1) The air filter of claim 1 wherein the nonwoven fibrous filtration web exhibits a particle Filtration Efficiency of at least about 50%. ### Claim 13 (depends on 1) The air filter of claim 1 wherein the at least one sorbent-free area of the nonwoven fibrous filtration web comprises at least one region that is a passivated region that is configured to provide a visual baseline zone of the air filter. ### Claim 14 (depends on 1) The air filter of claim 1 wherein the air filter is a high bypass ratio air filter comprising a conformable, unframed air filter media that is configured to be installed on a portion of an upstream face of a filter-support layer of an air-handling system, in a high bypass ratio configuration in which the air filter media occupies less than 85% of a nominal air-transmissive area of the filter-support layer. ### Claim 15 (depends on 1) The air filter of claim 1 wherein the air filter media is conformable into an arcuate shape so that the filter media can be installed on an upstream face of an arcuate filter-support layer of an air-handling system. ### Claim 16 (depends on 1) The air filter of claim 1 wherein the filter media is pleated and wherein a perimeter support frame is mounted to a perimeter of the filter media. ### Claim 17 (depends on 1) The air filter of claim 1 wherein the filter media is unpleated. ### Claim 18 (depends on 1) The air filter of claim 1 further comprising a nonwoven fibrous cover web that is affixed to the nonwoven fibrous filtration web so that sorbent particles of the at least one sorbent-loaded area of the first major surface of the nonwoven fibrous filtration web are present as a layer that is sandwiched between the first major surface of the nonwoven fibrous filtration web, and a major surface of the cover web, wherein the cover web exhibits an area density of less than about 20 grams per square meter and a thickness of less than about 1 mm and is at least substantially impenetrable by the sorbent particles. ### Claim 19 (depends on 1) The air filter of claim 1 wherein at least some fibers of the nonwoven fibrous filtration web are comprised of melt-processable polymeric resin that includes a white pigment. ### Claim 20 (depends on 1) A method of installing, visually monitoring, and replacing an air filter, the method comprising: a) installing the air filter of claim 1 in an air-handling system; b) periodically visually inspecting the air filter so as to ascertain how closely a visual appearance of the at least one sorbent-free area approaches a visual appearance of the at least one sorbent-loaded area; optionally repeating step b) one or more additional times; and, c) when the visual appearance of the at least one sorbent-free area is observed to approach the visual appearance of the at least one sorbent-loaded area to a particular degree, removing the air filter from the air-handling system.